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Date:   Thu, 15 Jun 2023 19:37:21 +0200
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Subject: Re: [PATCH v6 00/22] Restructure RPM SMD ICC
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To:     Stephen Boyd <sboyd@kernel.org>, Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Evan Green <evgreen@chromium.org>,
        Georgi Djakov <djakov@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Rob Herring <robh+dt@kernel.org>
Cc:     Marijn Suijten <marijn.suijten@somainline.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-clk@vger.kernel.org, linux-pm@vger.kernel.org,
        devicetree@vger.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Stephan Gerhold <stephan@gerhold.net>
References: <20230526-topic-smd_icc-v6-0-263283111e66@linaro.org>
 <0764b5fda92acb995ffbd05c4b3d2b2f.sboyd@kernel.org>
 <8568eead-90f6-ce15-d483-4d72dbab6294@linaro.org>
 <f526046568e6bbc8dc567109e6911f65.sboyd@kernel.org>
From:   Konrad Dybcio <konrad.dybcio@linaro.org>
In-Reply-To: <f526046568e6bbc8dc567109e6911f65.sboyd@kernel.org>
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On 15.06.2023 19:35, Stephen Boyd wrote:
> Quoting Konrad Dybcio (2023-06-15 00:52:07)
>> On 15.06.2023 02:49, Stephen Boyd wrote:
>>> Quoting Konrad Dybcio (2023-06-14 11:04:19)
>>>> This series reshuffles things around, moving the management of SMD RPM
>>>> bus clocks to the interconnect framework where they belong. This helps
>>>> us solve a couple of issues:
>>>>
>>>> 1. We can work towards unused clk cleanup of RPMCC without worrying
>>>>    about it killing some NoC bus, resulting in the SoC dying.
>>>>    Deasserting actually unused RPM clocks (among other things) will
>>>>    let us achieve "true SoC-wide power collapse states", also known as
>>>>    VDD_LOW and VDD_MIN.
>>>>
>>>> 2. We no longer have to keep tons of quirky bus clock ifs in the icc
>>>>    driver. You either have a RPM clock and call "rpm set rate" or you
>>>>    have a single non-RPM clock (like AHB_CLK_SRC) or you don't have any.
>>>>
>>>> 3. There's less overhead - instead of going through layers and layers of
>>>>    the CCF, ratesetting comes down to calling max() and sending a single
>>>>    RPM message. ICC is very very dynamic so that's a big plus.
>>>>
>>>> The clocks still need to be vaguely described in the clk-smd-rpm driver,
>>>> as it gives them an initial kickoff, before actually telling RPM to
>>>> enable DVFS scaling.  After RPM receives that command, all clocks that
>>>> have not been assigned a rate are considered unused and are shut down
>>>> in hardware, leading to the same issue as described in point 1.
>>>
>>> Why can't we move the enable of DVFS scaling call to the interconnect
>>> driver as well? We want the clk driver to not reference the interconnect
>>> resources at all.
>> That would result in no rpmcc ratesetting on platforms without a functional
>> interconnect driver. The DVFS call concerns both bus and !bus clocks.
>>
> 
> That's the intent. Probe the interconnect driver to get bus clk rate
> setting.
> 
> What are the !bus clocks managed by RPM?
Depending on the platform, that includes IPA, GPU, OCMEM, RF.. everything
that's not been separated out in patch 18.

Konrad